This invention relates to thermoplastic injection molding machines and, more particularly, to injection stretch blow molding machines wherein a finished article is released from the machine at an eject station to a container or conveyor for further processing. In particular, the present invention relates to improvements which make various components of the eject station quickly interchangeable to adapt the station for handling production runs of different blow-molded articles.
Injection stretch blow machines make hollow preforms and then convert such preforms into finished articles before the preforms leave the machine. Typically, a turret-like rotation plate on the machine indexes a set of thread splits through multiple stations including at least an injection station, a stretch blow station, and an eject station. Some machines also include a conditioning station between the injection station and the stretch blow station.
At the injection station hot molten thermoplastic material is injected into a set of preform molds with which the thread splits are associated so that after the injection cycle is completed, the preforms remain gripped by the thread splits on the rotation plate for indexing to the next station. At the stretch blow station, the preforms remain gripped by the thread splits but are then subjected to mechanical and pneumatic stretching through an internal stretch rod and internally introduced air pressure to expand and fill a hollow mold at that station. Finally, the rotation plate indexes the thread splits and their articles to the eject station where the thread splits are separated to release the articles.
The eject station includes a pneumatically operated, vertically reciprocable eject head that, by cam operation, separates the thread splits during an ejection stroke and physically contacts the finished articles with devices known as eject cores to encourage the articles to drop from, rather than adhere to, the thread splits when the splits separate. Due to the fact that the same machine is used to run many different products, the eject cores and the structure that mounts and guides them must be frequently removed and replaced with different components that are compatible with the specific product being run at the time. Different products may require a different number of mold cavities or have different neck finishes that necessitate this change over.
However, many of the components at the eject station are massive and unwieldy. Thus, in conventional machines, changing over the eject station from one production run to another is a very laborious, time-consuming, and unpleasant procedure. Typically, a worker must actually climb up on the machine, disassemble the eject station, and lift heavy components to one side in order to have access to parts that need to be changed out. Then he must lift and reassemble the apparatus back into position when the new parts have been installed. Obviously, the machine must be idle during this change-over, and the protracted delay can seriously reduce the productivity of the production facility.
The present invention provides a safe, quick and easy way of changing out the necessary components at the eject station each time a new product run requires such change. Rather than requiring complete disassembly of the eject station, including its heavy, cast-iron crosshead and pneumatic actuator, the present invention contemplates merely removing a few threaded fasteners, detaching a few relatively light-weight components from one another, and replacing one or more adaptor plates of the apparatus with a different set of adapter plates that correspond to the specific number and location of mold cavities for the new production run. Instead of replacing the entire eject core mounting plate of the station with a new mounting plate having a different number of eject cores, the present invention contemplates always using the same universal mounting plate for all mold cavities and then simply interchanging quickly and easily detachable adaptor plates that effectively modify the mounting plate to receive an appropriate number of corresponding new eject cores.